Magnetic heads for recording and reproducing signals



June 1960 HANS-OTTO G. LEILICH ,93

MAGNETIC HEADS FOR RECORDING AND REPRODUCING SIGNALS Filed Dec. 23, 1954 2 Sheets-Sheet 1 HANs-o'r'ro G. LEILICH 2,939,920

June 7, 1960 MAGNETIC HEADS FOR RECORDING AND REPRODUCING SIGNALS 2 Sheets-Sheet 2 Filed Dec. 23, 1954 Uni S ate P ent-O MAGNETIC HEADS FOR RECORDING AND nnpnonucmc SIGNALS Hans-Otto G. Leilich, Munich,

Stifterverband fiir die deutsche sen Bredeney, Germany Germany, asslgnor to Wissenschaft e.V., Es-

to magnetic heads and. is more with heads for magnetically The invention relates particularly concerned recording and reproducing signals in form of small magnetic dots on a fast moving signal carrier for use in magnetic storage devices of electronic computers and calculators.

It is an object of the present invention to provide a magnetic head for producing a large number of signs. or signals per unit length in the direction of movement of the signal carrier and to form the magnetic head in such a manner that its dimensions in the direction of movement of the signal carrier as well as vertically thereto are as small as possible so that a large number of magnetic heads may be arranged within a restricted space. The magnetic carrier may be arranged at the periphery of a rotating drum so that it moves in tangential direction while the direction vertically thereto is parallel to the .aXisof the drum.

It is a further object of the invention to provide a magnetic head producing a magnetic recording or reproducing field which is focussed as sharply as possible in the tangential direction so that a large number of mutually independent signals may be recorded on the circular trace. The dimension of the magnetic field in axial direction should not be to short in order. that the field may comprise sufiicient energy. In general a magnetic field in the shape of of .the knife is lying in axial direction.

It is a further objectof the invention to provide a magnetic head adapted to fulfill these requirements and which is as small as possible in axial as well as in tangential direction so that a largenumberof heads can'be arranged over the circumference of the magnetic drum.

The magnetic heads of the present invention should be well distinguished from the known sound heads, used for sound recording and reproduction inasmuch as the magnetic heads of the present invention are designed for higher recording and reproducing speeds and the magnetic field is focussed more sharply while at the same time the heads do not touch the magnetic carrier, a small distance or air gap the carrier. such a manner that a linear function exists between the current in the winding and the magnetic effect in the sound carrier; this is, however, not necessary for the purposes of the invention and themagnetic'heads may be designed in such a manner that this function is non-linear.

It is a further object of the inventionto provide a magnetic head for reproducing a sign'al'when the polarity of a dot shaped-magnetization at a well defined narrowly limited space of-the signal carrier changes.

According to the invention a loop or core of highly permeable magnetic material is fixedly held near the gap by cylindrical or conical supporting means. This supporting structure in which the loop can produce its full magnetic effect has the advantage that the dimensions of the gap are exactly defined and stable so that the magnetic being provided between the, head and The sound heads'are desig'nedusually in I a knife edge is desirable in which the edge 2 head produces a sharply focussed magnetic field at a well defined location of the signal carrier.

According to the invention the magnetic loop carries a coil comprising a high number of windings so that a transformer in the immediate neighborhood of the magnetic head can be avoided and connecting lines having a length of several feet may be employed in connection with this head.

According to the present invention the holding means may comprise clamping jaws holding the loop by pressure of a clamping member for instance a clamping ring which is simply pushed over the holding means so'that the use of screws is avoided.

The sensitivity of the magnetic head may be increased according to the invention by including a number of thin sheets of a highly permeable material in the loop, said sheets being formed and arranged in such a manner, that the number of sheets increases with the distance from the gap.

Other objects, advantages, and features of the present invention will become more fully apparent from the following description of preferred embodiments thereof taken in conjunction with the appended drawings, in which:

Fig. l is a schematic cross-section through the lower end of the magnetic head; a

Fig. 2 is a section through a loop or core consisting of a number of strips of sheet metal;

Fig. 3 is a longitudinal section through the magnetic head with the supporting member and Figs. 4, 5 and 6 show longitudinal sections and a ground plan of the magnetic head.

Referring first to Fig. 1 the magnetic head is arranged near a signal carrier 1 moving in the direction of the arrow 2 but separated from the head by an air gap so at it is not touching the magnetic head. The air gap may have a dimension of 0030:0005 mm. between the head and carrier. The head includes clamping jaws 3 supporting the loop meme 4 of magnetic material, and a spacer element 5 consisting of non-magnetic material arranged in the gap between the ends or poles of the loop. The poles of the loop have a width of approximately 0.1 mm. measured at the point lying adjacent to the signal carrier and including the spacer element 5. The loop 4 carries a coil 6. The coil 6 may have 50 windings of copper wire so that the head has an impedance of 70 ohms.

The loop 4 is shown in Fig. 2 on an enlarged scale. It consists of a number of strips 7, 8 and 9 of sheet metal. These strips extend'up to the gapof the loop. The loop includes furthermore strips 10 and 1 1- ending a short distancefrom the gap. The strips 10 and 11 have a shorter length than the strips 7, 8 and 9 'so that the number of strips increases with increasing distance from the P- Fig. 3 shows a section through the complete head having the form of a cylindric rod with a diameter similar to that of a lead pencil. The head comprises a metallic ring 14. The ring 14 is pushed so far tapering conical outer surface 13 carrying :a clamping upwardly over the tapering surface that it exerts a pressure upon the clamping jaws sufiicient to secure the loop 4 in its place and to-holdit stationary under all conditions of use. The clamping jaws grip the loop near its poles or ends so that these ends cannot vibrate or change their positions under the influence of forces acting upon the loop during the operation of the heads.

The coil 6 has connecting wires extending upwardly into the casing 12.

and 17 consisting for instance These wires are soldered at the places 15 to two connections 16 -n ltwillzhe-under tood, th 'described'head are possible without departing o iLitz w r .auder ending utward ynithesaeia casing lgis closed at its upper end by an insulating ele- 'ment"18h'aving-holes for receiving the connecting wires ahead carrier {not shown) so that :the magnetic head m y e aligned and tezraet y adj ed with I na ner. Ih ieomp et ma neti .heat hee h .Y' y

small diameter of ;for instance /4 ,soithat ,alarge ,nurnber of heads may be arranged in close relation on the head carrier.

' Figs- 4 and sshewthe neeie rehe eo thee n .12 a :-the lower. end ath reqf- 11 :Q .g ha pe orr eeivin-gtheaeei an th uppe 1P, magnetic loop. A metal screen 20 i s';-arr anged. between the loop a d the casing: Thi s ree ha th iefieei ith the'magnetic,fieidds:QQBQQ PE ESU 1 65? den changes otmagnetizat ouoeeu and sha l r v the disadvantages of a stray flux.

ttma y ariatio sq sheiaho e from the scope pfzthe present invention;

What I l imiist LA magn ic ahea fo pr uci mi u e manned; gn ti ab e .tan ia y rfla signal carrier, comprising a loop of magnetic material of h gh pern1eahility, anapi nsai loop, lasp ee uea gap, two poles formed by the end :Qf said'rnagnetic material adjacent .said vspa er, en el. heated nan-magne i holding element in form o ,f ajhollow r d of sub tan i l y cylindrical press-section, its axis be ng pos ti n d stantially perpend cular togthe signal,carriernsaid-hqllqw r d h ving i ip ri ion of red ce ou r di met rrg t end directed towards thesignaLcarrier,,polepieee dapted to -elam-p said poles at ;the extremity of said po on of reduced. di me e a lot separ ing sa --p nie es, an extendingthroughout said portion of ,IQdI Rd diameter for rec iving th v1 0p an clam in :mean -disp s d in slip-on relation 10 "the por ion otireduced outer diameter ofsaid holding element, s id d mping .m an h ving dimensionsnot to exceed a cylin ric l surface coincident .Withthe outer surface of aid holl w :rod.

-2. A magn i :head for pro u i g iniinute. magne ic signs on a 'fast rmoving ,rnagnetizahle-.substantial1y:flat signal carrier, comprising a loop of magneticmaterial of r h g -rpermeability, azigap .iI1.-1S1id loop, ;a.-spac.e.r in said g p, tworpoles ifQrmQ by the nds of s d magneti I materialradiacent said spacer, ranelonga-tednommefigetio holding element in form of a hollow rod of substantially cylindrical gross-section, its axis being positioned -sub stantially perpendicular to the signal carrier, ,saidqhollow rod haying ,.a portion ,of reduced outer diameter at :the

and directed towards the signal .carr'ier, ipole. ipieces' adapted to clamprsaid poles at the egrtremityof said por- .tionof reduceddiameter, aslot separating said polepieces and extending throughout said portion of reducedrouter diameter for receiving the loop and clamping means disposed in slip on relation ,on-the :portion of reduced outer diam t r of said h lding element, said clamping ,rneans having dimensions-not to exceed a cylindrical surface coincidentwit-h'the outer surface ,of said hollow rod, a coil on said -loop, the,l-argest dirnensionof said coil ex.- .tendingin-the direction of the longitudinal axis of said holding element.

A magnet h ad r produ ng minut mag etic signs on a' fast moving rr agne' zabl e substantially flat si n ea ner emu s h a leap o a n t c mate i 10f gap, two poles formed by therends of said magnetic mate-' rial adjacent said spacer, an elongated non-magnetic holding element in form of a hollow rod of substantially cylindrical cross-section, itseaxis being positioned substantially er endieu a t thee a ee r r saidhnl owr having a portion--with;ataper diameter at the end directed towards the-signal carrier, n jnie e s anted its leanse oles a t extremit q i a d per-tita of e ueed di meter, ,-a slot separating said pole pieces and extendmg throughout .said tapering portion for ,receiying the iloop and ,a clamping ring dis posed coaxially on 'and adapted to engage" said tapering teeethe ehy :te d pressiseid-nol nie e i hfly a in the poles of sai opp.

4 A magnetic 'headfor producing minute magnetic signs on a fast moving magnetizable suhstantially flat signal carrier, comprising-i-a l'oop of magnetic material of high perrneability, a gap in said loop, =a-spacer=in said gap, .two poles formed by {the ends of said magnetic mate rial adjacent said spacer, an elongated non-magnetic holding element in form of a hollow rod of substantially cylindrical cross-section, its axis being positioned -substantially perpendicular to the signal carrier, said hollow rod having a portion of reducedouter diameterat'lthe end directed. towards :the-signal carrier, pole pieces adapted to clamp said poles at the'extrernity of -=said portion of reduced diameter, a slot separating said -po'le pieces and extending throughout said portion of reduced outer diameter for receiving the loop and clarnping -means disposed in slip-on relation onthe portion of reduced outer diameter of said hollow rod, said clamping means having dimensions to lie within a cylindrical surface-coincident with the .outersurface of-saidhollowrod, 'a coil on'said loop, the largest dimension of said coil extending in-= the direction. of :the longitudinal axis of. said holding element and a metallic shield between the coil andsaidpoles, said shield extending beyond the dimensions of the coil in the direction transverse to the movementofthe *signal carrier.

:5. A magnetic :headgas in claim 2, whereineaid pole pieces are outwardly defined by two pairs of symmetric planes, the respective planes of ,symmetry of both pairs intersecting -at a right angle, said intersection 'being -c oaxial with the axis of -saijd hollow rod,-one-pa ir-of planes being inclined at an angle of substantially 10* to thesignal carrier and intersecting to a'lengthwhichis subst-an tially that of-=the width of said poles, the other pair of planes being inclined at an angle of substantially "-60" to the signal carrier :and 'interescting the'ends of s aid length. I

6. A magnetic :head' as in claim 5, wherein said" loop of :magnetic material'is mountedinside of said pole pieces 'definedlby said two pairs'of symmetrical planes;

' ReferencesJCited inthe fileofzthis patent UNITED STATES PATENTS: 7 3 ,252 a, 9 89 67 L 1: 5 2,144,844 I 1939 2 4 9 R M y 0 94 -2 6 3 fia ra -,-i-,---t-.----- ,S n 2. 1.9 3 2,668,873 -Ml 0 i 19.

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